Hydrocarbon fuels contain sulfur compounds which form sulfur oxide during a combustion process and eventually lead to sever issues in environment and health of human. Also, higher concentrations of sulfur compounds results in acidic rains. Furthermore, when the concentration of sulfur in oil derivatives exceeds an allowable value, it leads to corrosion of metallic vessels, reactors, tubes and joints, and poisons the high-cost down-stream catalysts in addition to polluting the atmosphere. Considering the above-mentioned facts, desulfurizing the oil cuts is an essential process in hydrocarbon fuels processing.
Desulfurization of sulfur containing solutions is performed through Hydrodesulfurization (HDS) and nonhydrotreating desulfurization processes. The nonhydrotreating desulfurization processes include extractive, oxidative desulfurization (ODS), adsorption, biological desulfurization (BDS), etc. which are known to be complementary to HDS process. The catalytic oxidative desulfurization may be an appropriate alternative to HDS process, since this method is carried out in normal reaction conditions such as atmospheric pressure and low temperatures in which there is no need for hydrogen. However, catalytic oxidative desulfurization processes require one or more oxidizers such as organic peroxides, hydroperoxides, peroxide salts, nitrogen oxide, oxygen (O2), hydrogen peroxide and tetra butyl hydrogen peroxide, etc., which decrease safety of the sweetening process due to their low stability and complicated conditions for their maintenance in reaction environment. Additionally, these oxidizers have a high cost making it not cost effective to conduct the catalytic oxidative desulfurization process.
The catalysts used in oxidative desulfurization process include heterogeneous and homogenous catalysts. In desulfurization processes which adopt homogenous catalysts, catalysts such as formic acid and acetic acid, etc. are utilized. However, the efficiency of the desulfurization in these processes is low and an adequate standard amount of safety is not provided. In the desulfurization processes using heterogeneous catalysts, a solid catalyst is utilized along with the oxidizer agent in which the active catalyst is supported over catalyst supports such as alumina, silica, etc. Alternatively, the solid catalyst is used solely. However, supporting the catalyst over catalyst supports involves low surface area, low pore volume, no-uninform distribution of the active catalyst, and possibly the agglomeration of the metallic particles; consequently, it is not an easy task to impregnate the catalyst support by high amount of metallic particles which is necessary for desulfurization of a fuel feedstock containing dibenzothiophene and alkyl dibenzothiophenes.
Hence, there is a need for an oxidative desulfurization process and catalyst which may overcome the high cost and low efficiency of common oxidative desulfurization procedures. Also, there is a need for an oxidative desulfurization process and catalyst to alleviate the reaction conditions (atmospheric pressure and low temperature) for oxidative desulfurization and also reduction of the consumption of catalyst while increasing sulfur reduction efficiency. Additionally, there is a need for utilizing a catalyst for oxidative desulfurization of fuels, which may not involve the agglomeration of catalyst and may facilitate the formation of active sites over the catalyst. Moreover, there is a need for a method for oxidative desulfurization that may utilize suitable and optimized process conditions.